Sandwiched between the Great Lakes, Michigan features some of the most extreme weather in the United States. While most are familiar with Michigan’s lake-enhanced winters, a less-appreciated aspect of Michigan's climate is that the southwestern corner of the state exhibits tornado frequencies on par with much of tornado alley. The intensity of these weather extremes can wreak havoc on the Michigan power grid. Michigan’s major power providers have struggled to contain outages as the aging, exposed power infrastructure is repeatedly subjected to severe weather. The resulting sustained power outages have resulted in legislative penalties and fines for Michigan utilities, as well as increasing rates for their customers to fund resilience initiatives.
May 7, 2024 provides an interesting case study for how Michigan’s power systems responded to a unique weather occurrence: it’s first tornado emergency. Tornado emergency labels are enhanced versions of tornado warnings that are reserved by the National Weather Service (NWS) for the most serious of circumstances. Typically, a large and destructive tornado must be confirmed to be on the ground and heading towards a populated area, posing a catastrophic threat to life and property. Often, these tornadoes are classified as strong-to-violent (EF2-EF5 on the enhanced Fujita scale, or winds well over 100 mph). Here, we present data from StormImpact’s national power outage monitoring system to demonstrate the efforts of three Michigan utilities in this historic weather event.
Michigan’s tornado emergency occurred primarily in Portage, Michigan, a city of nearly 50,000 within Kalamazoo County. This high-end EF2 tornado was on the ground from 5:55-6:17 PM, recording winds of 135 mph for 11 miles. This event occurred within the context of over 70 other reported tornadoes within the region (Figure 1), including a strong EF2 in St. Joseph and Branch Counties directly south and southeast of Kalamazoo County.
Figure 2 shows the NEXRAD radar imagery of supercell motion over southern Michigan and the corresponding customer outages. The cells which produced the St. Joseph/Branch tornado and the Kalamazoo County tornado emergency move in tandem, causing extensive damage to local power infrastructure. Elsewhere, strong storms in extreme southwestern Michigan cause modest, short-term outages in Berrien County. As storms reach eastern Michigan and the Detroit metro, high winds cause elevated outages in Macomb County.
The two largest utilities in Michigan are Consumers Energy and DTE Energy, serving ~1.9 million and 2.2 million customers, respectively. Indiana Michigan Power, a subdivision of American Electric Power (AEP), serves northern Indiana and parts of southern Michigan and hosts 130,000 customers in Michigan. Figure 3 shows power customers affected for each utility in the region. Minor outages in the region are initially reported preceding the tornado emergency. However, by around 5 PM when the tornado event begins, Consumers Energy experiences a considerable surge in reported outages up to over 25,000 regional customers. Shortly thereafter, DTE Energy begins to record outages of 5,000 customers. For context, Table 1 shows the number of customers served for these utilities for selected Michigan counties.
It is evident that this event had a significant impact on Consumers Energy. As the tornado emergency transpires in Kalamazoo County, their customers quickly represent the bulk of Michigan power customers out. However, the data shows that Consumers quickly begins restoration efforts, and a five-fold reduction in customers affected is achieved within 24 hours.
Further to the south in St. Joseph County, the main power provider is Indiana Michigan Power. Here, the separate EF2 tornado-related disruption to Indiana Michigan Power customers was contained to a peak of about 1,500 customers, or about 12% of their customers in St. Joseph County. Moreover, power was quickly restored, dropping to about 200 customers out within two hours. We cannot say from the data available why St. Joseph County escaped the more extensive power outages that were experienced in Kalamazoo County; however, it is worth noting that St. Joseph County is more rural (<20% of the customers in Kalamazoo County), and therefore a damaging tornado is less likely to strike critical power infrastructure.
As the storm system progressed eastward into the Detroit metro, primarily served by DTE Energy, notable outages were constrained to Macomb County. While no tornadic storms were reported in the Detroit metro, Figure 1 shows that wind-related damage was reported in near Macomb County, likely causing the outages visible in the data. Only 1.3% of Macomb customers were affected by this event (Figure 4), which translates to about 5,000 customers given the higher population of the metro area.
The path of tornadoes is largely unpredictable, and no utility company can expect to withstand total operational control under the conditions of violent tornadoes. As Michigan moves towards a more resilient power grid, its response to major weather events will require continued analysis.
To learn how StormImpact can help utility companies prepare for inclement weather and to better understand their risk, contact us today!
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